Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$106.41	3.216%	$109.8321	$109.83	$109.85	$109.80
Purchase #2	$117.57	8.554%	$127.6269	$127.63	$127.65	$127.60
Purchase #3	$204.28	11.362%	$227.4903	$227.49	$227.50	$227.50
Purchase #4	$214.98	7.178%	$230.4113	$230.41	$230.40	$230.40
Purchase #5	$41.95	3.688%	$43.4971	$43.50	$43.50	$43.50
Purchase #6	$108.48	10.458%	$119.8248	$119.82	$119.80	$119.80
Purchase #7	$204.75	8.874%	$222.9195	$222.92	$222.90	$222.90
7 purchase totals =	$998.42		$1,081.6020	$1,081.60	$1,081.60	$1,081.50